Ophthalmological Laser Treatment Device

ABSTRACT

An evaluating unit which is adapted to determine a degree of an instantaneous overlap between an optical zone of the eye and the structure, or at least a part of the structure effecting refractive correction, based on a recorded image. By determining the degree of overlap between the instantaneous optical zone and the structure to be introduced, it is possible to control the superposition of the optical zone with the tissue volume which is specifically altered by means of the laser cutting and, accordingly, to enable a maximum coverage.

The present application is a continuation of U.S. patent applicationSer. No. 13/635,999 filed on Nov. 16, 2012, which claims priority fromPCT Patent Application No. PCT/EP2011/001319 filed on Mar. 17, 2011,which claims priority from German Patent Application No. DE 10 2010 012616.0 filed on Mar. 20, 2010, the disclosures of which are incorporatedherein by reference in their entirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention is directed to an ophthalmological laser treatment devicehaving a treatment laser, particularly an excimer laser or a femtosecondlaser, for introducing energy into a portion of an eye of a patientaccording to a predetermined surgical structure to be generated in theeye, a light source for illuminating at least the portion of the eye,and a detection device for recording an image of at least the portion ofthe eye, and to a method for introducing energy into an eye according toa predetermined surgical structure by means of an excimer laser or afemtosecond laser, particularly an operating method for anophthalmological laser treatment device which has a treatment laser anda detection device for recording an image of the eye.

The surgical structure can be predetermined, for example, in the form ofirradiation control data sets such as shot position, shot intensity andshot frequency. Alternatively, it may be a matter of more abstract datasuch as parameterized spatial curves which, as a preliminary step forirradiation control data, describe the incisions to be made. Thesurgical structure to be generated in the eye may also be represented inany other suitable form. A digital camera, for example, can be used asdetection device.

It is noted that citation or identification of any document in thisapplication is not an admission that such document is available as priorart to the present invention.

Ophthalmological laser treatment devices can be used to perform lasersurgical procedures on the cornea such as femtosecond lenticuleextraction (FLEx), in particular small incision femtosecond lenticuleextraction (SMILE). A corresponding femtosecond laser system isdescribed in WO 2008/064771 A1. In this case, the removal of stromaltissue required for refractive correction is separated by a twofoldlaser cutting for preparing a lenticule. In so doing, the zone of theactual refractive correction (hereinafter: correction zone) is entirelycontained within the lenticule, but the lenticule can be greater thanthe correction zone. The size of the correction zone and the size of thelenticule are so selected depending on optical and physiological factorsthat the refractive correction in the correction zone does not dependupon the situation in the transition from the edge of the correctionzone to the edge of the lenticule. For example, shape matching may berequired in this case so as to rule out any contribution to therefractive correction.

The lenticule can then be removed with the help of forceps after openinga corneal flap covering the incision area or, alternatively, through asmall lateral laser incision. Only a femtosecond laser system isrequired for this purpose. Alternatively, it is known, e.g., from US2006/0155265 A1 to cut a corneal flap using a fs laser system and thento perform refractive corrections in the cornea under the lifted flapusing an additional excimer laser. The corneal flap is then closedagain.

Another possibility for improving defective vision by laser surgery isknown from WO 2006/051364 A1. In this method, deep cuts are made instromal tissue by a femtosecond laser to produce a contiguous cavity,particularly with a cylindrical shape, without ablation of tissue. Whenthe cavity collapses, the cornea relaxes due to the reduced tissuestrength and intraocular pressure and assumes a new shape with alteredcurvature.

In general, there exists the need for the structure which is to beintroduced into the eye by excimer laser or femtosecond laser to beexactly positioned in the coordinate system of the laser. The requiredaccuracy depends on the type of treatment. If there is no correction ofaberrations of a higher order than sphere and cylinder, the accuracyrequirement with skillfully constituted surgical structure (alsoreferred to as “profile”) is low, i.e., about 0.2 mm.

WO 2008/055604 A1 describes how the eye to be treated can be positionedrelative to the treatment laser by displacing a support device for thepatient by recording monitoring images of the eye and detection of thepupil. For this purpose, the actual position of the pupil is comparedwith a predetermined reference position and a displacement iscalculated, for example, between the actual center and reference centerof the pupil. This displacement can either be compensated automaticallyby a movement of the support device or the operator can be giveninstructions for a manual compensating movement.

In spite of the displacement compensation, suboptimal treatment canresult so that vision is not optimal, particularly in dark environments.

It is noted that in this disclosure and particularly in the claimsand/or paragraphs, terms such as “comprises”, “comprised”, “comprising”and the like can have the meaning attributed to it in U.S. Patent law;e.g., they can mean “includes”, “included”, “including”, and the like;and that terms such as “consisting essentially of” and “consistsessentially of” have the meaning ascribed to them in U.S. Patent law,e.g., they allow for elements not explicitly recited, but excludeelements that are found in the prior art or that affect a basic or novelcharacteristic of the invention.

It is further noted that the invention does not intend to encompasswithin the scope of the invention any previously disclosed product,process of making the product or method of using the product, whichmeets the written description and enablement requirements of the USPTO(35 U.S.C. 112, first paragraph) or the EPO (Article 83 of the EPC),such that applicant(s) reserve the right to disclaim, and herebydisclose a disclaimer of any previously described product, method ofmaking the product, or process of using the product.

SUMMARY OF THE INVENTION

It is the object of the invention to improve an ophthalmological lasertreatment device and a method of the type mentioned above so that visionis improved after a laser surgical treatment.

The invention provides an evaluating unit which is adapted to determinean instantaneous degree of overlap between an optical zone of the eyeand the structure, or at least a part of the structure effectingrefractive correction, based on a recorded image. In connection withtreatment of the cornea, the optical zone is the projection of thepupillary aperture (particularly open to the maximum extent) on thecornea or most often generally that region of the tissue to be treatedthrough which light arrives in the eye via the pupillary aperture(particularly open to the maximum extent) and can contribute to imaging.Accordingly, the instantaneous overlap depends upon the degree to whichthe pupil is open at that instant. Further, according to the invention,the determined degree of overlap can be taken into account in at leastthe step of determining the irradiation control data and/or the step ofdeciding to start irradiation of the eye. The degree of overlap can bedetermined, for example, as a one-dimensional or multi-dimensional value(scalar, vector or higher-order tensor).

According to the invention, it was recognized that, regardless of thetype of positioning (fully automated, semi-automated or manual), bydetermining the degree of overlap between the (instantaneous) opticalzone and the structure to be introduced, or at least the part of thestructure effecting refractive correction, the coverage of the opticalzone can be monitored by means of the tissue volume that is specificallyaltered by the laser treatment and accordingly a complete coverage ismade possible, which is important for a successful refractive treatmentwithout vision impairment. If there is no monitoring of the overlap, asis the case in the prior art, vision may be impaired under low ambientbrightness. When the comparison of the overlap of the pupils and thetreatment geometry is carried out automatically, the user can fullyconcentrate on the task of centering.

The structure to be introduced can involve, for example, a tissue volume(lenticule) to be removed manually following the laser treatment. It canalso involve, for example, an incision pattern for radial keratectomy orcylindrical or conical incisions. These structures usually have a centerof symmetry which should be positioned approximately in the center ofthe optical zone. Structures of this kind to be introduced often have noincisions in the center of the structure.

The evaluating unit for determining the degree of overlap preferablydetermines an area of the pupil based on the recorded image and an areaof the structure, or at least of the part of the structure effectingrefractive correction, and an intersection between the two areas. Theshape and position of the pupil are advisably determined in order todetermine the pupil area. The areas can be determined, for example, asscalars (amount of area in question), as plane outline curves, asparameterized spatial vector area or as point clouds of discretesampling points. Based on the intersection, the degree of overlap can bedetermined in an economical manner, for example, by determining thequotient from the area size of a plane projection of the intersectionand the area size of the pupil. The imaging scale of the recorded imagemust necessarily be taken into account when determining the areas andthe intersection.

The evaluating unit is advantageously adapted to identify and locate acharacteristic of the eye in the recorded image and to determine arelative offset between a point of the characteristic and a point of thestructure. For example, the pupil, the pupil edge, the area centroid ofthe pupil, a best-fit circle or a best-fit ellipse can be identified ascharacteristic. In particular, the offset or an oppositely directedoffset of the same magnitude and/or the degree of overlap can beindicated visually and/or acoustically. The offset can advantageously beused in assessing the overlap situation.

In order to allow a sufficient coverage of the optical zone by thesurgical structure (hereinafter also referred to as treatment site), thestructure to be introduced, for example, edge cuts of a lenticule, canbe displaced and/or enlarged particularly until a complete overlappingwith the pupil is predicted. This can be carried out manually or in asemi-automated or fully automated manner (by the evaluating unit or acontrol unit). The enlargement of the treatment site (in this example,the actual correction zone within the lenticule diameter) relative tothe optical zone (particularly the maximum pupil diameter) by an amountcorresponding at least to the offset of the working center (lenticulecenter) relative to the center of the optical zone (scotopic pupilcenter) can be referred to as decentering.

Therefore, it is particularly advantageous when the evaluating unitdetermines and outputs a degree of suitability of the instantaneouscoverage situation between structure and optical zone based on thedetermined degree of overlap. This makes it easier for the operator toassess the coverage situation and the operator can accordingly reducethe duration of the treatment, which minimizes the likelihood of interimchanges in position on the part of the patient.

In preferred embodiment forms, the evaluating unit displays the recordedimage visually in superposition with a graphic representation of thestructure according to the determined offset. In this way, the operatorcan interpret the degree of superposition and particularly the coveragesituation better and faster overall, which further reduces the treatmenttime.

It is advisable that a support device is provided for the patient and apositioning device is provided for displacing the support device and/orthe laser; the evaluating unit controls the positioning device dependingon the determined degree of overlap between the pupil and the structureand/or depending on the offset between the characteristic and thestructure. Accordingly, the location at which the structure is generatedcan be displaced relative to the eye without changing the actualstructure to be generated. Only a translation of the structure iscarried out in the coordinate system of the laser. This allows anunsatisfactory overlap to be compensated in a semi-automated or fullyautomated manner and can likewise serve to shorten the treatment time.

In advantageous embodiments the evaluating unit compares a value of thedetermined degree to a predetermined threshold and outputs a hapticand/or visual and/or acoustic signal depending on a result of thecomparison. For example, the operator can be alerted about an acceptablecoverage or warned about an insufficient coverage. Alternatively or inaddition, the evaluating unit can compare a value of the determineddegree with a predetermined threshold value and, depending on a resultof the comparison, particularly also depending on a relative offsetbetween a characteristic and the structure, an irradiation of the eyecorresponding to the structure can be carried out, particularly when thetwo threshold values are identical. A comparison of this kind canadvisably take place after an offset between laser and eye has beencarried out to compensate for an unsatisfactory overlap. Provided theconditions for offset and overlap are met, this allows in particular afully automated treatment so that the probability of interim changes inposition on the part of the patient is minimized.

The eye is preferably illuminated by infrared light. Therefore, thepupil is open to the maximum extent so that the instantaneous opticalzone reaches its maximum size. Alternatively, the eye can be illuminatedby visible light for recording the image, and an intensity of the lightis determined and, based on an instantaneous area of the recorded imageand on the intensity, a maximum pupil area is predicted and is used fordetermining the overlap. Alternatively, when illuminating with visiblelight maximum pupil dilation can also be achieved through medication,although this will mean a temporary stress for the patient aftertreatment.

In preferred embodiment forms, the ophthalmological treatment devicecomprises a contact element for mechanically fixating the eye. Thecontact element, typically a contact glass, is advisably transparent tothe spectral region used for the therapeutic radiation. By fixating theeye mechanically, the risk of an erroneous positioning of the surgicalstructure in the eye can be reduced. The mechanical fixation is requiredparticularly with femtosecond lasers.

The degree of instantaneous overlap can advantageously be determinedbefore and/or after implementing the mechanical fixation. Determiningthe degree of overlap prior to fixation can assist in determining ashifting of the patient necessary for achieving a specified degree ofoverlap. To this end, for example, a degree of overlap can be predictedas a function of an offset by means of a computer simulation based on amathematical model. That offset for which a maximum of the degree ofoverlap is predicted can be determined subsequently, for example.Shifting of the patient followed by fixation of the eye can then becarried out automatically, for example, or only when actuated by theoperator. Alternatively, the shifting of the patient can be presented tothe operator merely as a suggestion. The operator must then initiate thefixation manually.

The corneal limbus is suitable as a definitive reference for eyemovement tracking with respect to the cornea. If it is not visible, onlythe pupil remains as principal geometric feature. However, thevariability of pupil size presents a drawback in this regard. As thesize changes, the center of the pupil also shifts. Therefore, it isadvantageous to track movements of the limbus during and/or after theprocess of anchoring to the contact element, since the limbus is in afixed relationship to the eye geometry. In particular, if the positionof the photopic and scotopic pupil center in relation to the limbus isknown, the position of the scoptopic pupil can be determined for anypupil diameter by interpolation and the overlap can be evaluated on thatbasis.

The invention also comprises a control unit which is set up to implementa method according to the invention. The setup can be carried out in aprogrammed manner, for example, by means of software modules fordetermining a degree of an instantaneous overlap between an optical zoneof the eye and the structure based on the recorded image and fordetermining irradiation control data and/or for deciding about beginningirradiation of the eye depending on the degree determined.

The invention is provided not only for application to the cornea, butcan be applied to all parts of the anterior portion of the eye, forexample, to the eye lens or the capsular bag.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B show an ophthalmological laser treatment device;

FIG. 2 shows a flowchart for a method for controlling a compensatingmovement; and

FIGS. 3A and 3B show variants for centering a lenticule.

Corresponding parts have the same reference numerals in all of thedrawings.

DETAILED DESCRIPTION OF EMBODIMENTS

It is to be understood that the figures and descriptions of the presentinvention have been simplified to illustrate elements that are relevantfor a clear understanding of the present invention, while eliminating,for purposes of clarity, many other elements which are conventional inthis art. Those of ordinary skill in the art will recognize that otherelements are desirable for implementing the present invention. However,because such elements are well known in the art, and because they do notfacilitate a better understanding of the present invention, a discussionof such elements is not provided herein.

The present invention will now be described in detail on the basis ofexemplary embodiments.

FIG. 1 shows an ophthalmological laser treatment device 1 for correctingdefective vision using laser radiation. The outer appearance is shownschematically in FIG. 1A. The treatment device 1 comprises a supportdevice 2 for a patient in the form of a table and a treatment laser 3having optics for positioning and focusing the laser beam in the area ofa treatment position at which a patient's eye can be positioned. Itfurther comprises a positioning device 4 which supports the table 2 andcan move it linearly in all three spatial directions. A microscope beampath which allows the operator to visually monitor the course of thetreatment in an observation eyepiece 6 is coupled into the beam path ofthe treatment laser 3 exiting the treatment head 5 which is arrangedabove the table 2.

The treatment device 1 further comprises as control unit 7 a computerhaving a keypad 8 and a monitor as display 9. The ophthalmologicaldevice 1 is controlled by means of the control unit 7. The laser 3 is afemtosecond laser, for example, so that a flap or a lateral extractionincision and a lenticule can be cut by the same laser. At its end facingthe table 2, the treatment head 5 has a contact element 10 in the formof a contact glass which touches the eye of the patient during treatmentand is spatially fixed relative to the treatment device 1. During theirradiation process, the laser beam is focused in the eye of the patientthrough the contact element 10. For example, the contact element 10 canbe plane or anatomically curved on the side facing the eye.

In alternative embodiment forms, an excimer laser can be providedinstead of or in addition to the femtosecond laser. When an excimerlaser is used exclusively, a contact element 10 can be dispensed with. Amovement tracking system which repositions the treatment laser 3 totrack possible eye movements of the patient during the irradiationprocess is advisable when using an excimer laser.

FIG. 1B shows the coupled beam paths of the treatment laser 3,microscope 6, detection device 11 and light source 12 schematically andin a highly simplified manner with respect to the optical construction.The detection device 11 is constructed as a camera by which the eye A ofthe patient is recorded through two beamsplitters 13, 14 and the contactglass 10 which is shown here at a distance from the eye A. Therefore, anobservation beam path 15 runs from the eye A through the contact glass10 and both beamsplitters 13 and 14 to the camera 11. The image taken bythe camera 11 is sent to the computer 7. Beamsplitter 13 allows the eyeA to be observed microscopically via the observation eyepiece 6. Thetreatment laser beam L can be directed from the laser 3 to the eye A viabeamsplitter 14 when the eye A is spatially fixated by means of thecontact glass 10 in order to carry out the desired correction ofdefective vision.

The light source 12 preferably emits exclusively infrared radiationbecause in this case the pupil can open wide and, in addition, ahigh-contrast video recording of the pupil can be carried out,particularly also when the iris is very dark. Alternatively or inaddition, however, the light source 12 can also emit visible light. Inparticular, the visible spectral component can be cut off by means of afilter (not shown). The light of light source 12 is reflected into themicroscope beam path by another beamsplitter 19, for example.

When the patient's eye is detected through the device 7, preferablyduring the process of contacting the contact element 10 or immediatelythereafter, the video image of the camera 11 is analyzed by theevaluating unit 20. To this end, it carries out a detection of the pupiland displays at least one geometric characteristic, for example, thepupil edge, area centroid, best circular fit or best elliptical fit, tothe user on the monitor 9 and/or in the eyepiece 6 in superposition withthe video image. In addition or alternatively, it compares a geometriccharacteristic with at least one treatment parameter, for example, thelenticule position, the position and shape of the correction zone of thelenticule, the lenticule diameter, the cutting angle, the flap diameter,the center of the flap, the position of the flap hinge, or the angle ofthe hinge, and/or a system parameter, e.g., the center of the treatmentsite, and determines a deviation from a predetermined ideal case anddisplays this on the monitor 9.

For example, when analysis is carried out by determining the area ratiosof the pupil and correspondingly scaled surgical structure, a degree ofoverlap between the structure to be generated, or at least the part ofthe structure effecting refractive correction, and the optical zone anda shift between the center of the pupil as exemplary reference point andthe center of the structure to be generated are determined. This can beused to control the positioning device 4 in such a way that the table 2and, therefore, the eye A of the patient lying on the table 2 can bemoved into a predetermined reference position relative to the contactglass 2. Alternatively, instead of the pupil center, any other eye-basedcharacteristic can be used to determine the displacement by identifyingand locating it in the recorded image. Reference is made to WO2008/055604 A1, particularly FIG. 3 and the accompanying remarks, withrespect to the description of the determination of displacement. Theimage recording and the identification and locating of thecharacteristic are advisably carried out repeatedly so as to allow forchanges in position of the eye. This also applies to the determinationof the instantaneous degree of overlap.

The area can be determined, for example, by counting picture elements(pixels) in digitalized images, for example, the pixels in theintersection set between determined pupil margin curves and thecorrection zone of the surgical structure. The ratio of the surface areaof the total pupil area to the proportion of the pupil area coincidingwith the correction zone gives the degree of overlap. This degree ofoverlap is 100% when the pupil is located completely within thecorrection zone. Further, the deviation of the centroids from thecorrection zone and pupil area, which gives information about theoverlap reserve (additional overlapping of the correction zone beyondthe pupil area), can be used for the degree of suitability. However, itis also conceivable to output a signal for a sufficient suitabilityalready when there is a partial overlap of only 90% or 95%, for example.

The accuracy of the comparison between treatment parameters andcharacteristic geometric quantities of the video image can be furtherimproved through additional adaptation of the scaling of the video imageand/or overlapped visualized treatment parameters. The scaling providesfor improved geometric congruency of the metric of the coordinatesystems to be compared. Further, the deviation can be evaluatedparticularly on the basis of whether the current position does notexceed a given threshold value for the decentering and/or a giventhreshold value for the overlap between the optical zone and thestructure to be generated.

For example, the evaluating unit 20 which is a software module of thecontrol unit 7, for example, displays on the monitor 9 the last imagerecorded in which the detected characteristic, in this case the edge ofthe pupil, is marked and the structure to be generated is superimposed.Optionally, the structure to be generated and the marking of thedetected characteristic can also be reflected into the microscope beampath so that the operator sees these criteria directly superposed withthe image of the eye A. In this way, the operator himself can see thedegree of overlap directly.

In a special embodiment, an automatic response of the device, forexample, a compensation of the detected displacement, can be initiatedbased on the evaluation.

The sequence of a method for movement control is shown schematically byway of example in the form of a flow chart in FIG. 2. The stepssubstantially correspond to those described in WO 2008/055604 A1,wherein the display data in steps S11, S22, S24 and S27 are displayedsimultaneously. For example, the detected pupil and the determineddisplacement are superimposed on the video image in identical scale andthe rest of the data are displayed alongside. Steps S26A, S27A and S28Awhich will be described in the following are carried out in addition. Inso doing, the structure to be generated is likewise superimposed withthe video image in the course of step S27A for displaying overlapping.As in WO 2008/055604 A1, the display can also be carried outadditionally or alternatively in the eyepiece 6; the video image isomitted in the eyepiece 6 because the optical image is availabletherein.

In step S26A, the instantaneous degree of overlap between the structureS and the instantaneous optical zone of the eye A is determined based onthe detected pupil as geometric characteristic and based on thepredetermined surgical structure S and is displayed, for example, byshading of the intersection between the areas of the structure Sprojected into the video image and the detected pupil P. The degree ofoverlap compared to a predetermined threshold value can be used in thecalculation of the correction in step S28. The threshold valuedescribes, for example, a minimum overlap to be achieved. If this can beachieved without movement, the process is aborted. Otherwise, thedetermined suggested correction is shown in step S28A with the otherdata, for example, as a displacement vector in the video image.

As an alternative to a fully automatic compensation movement, a signalcan also be displayed to the user. The signal can be haptic, optical oracoustic. In particular, there is provided a quantitative indication ofthe degree of deviation found, particularly a simultaneous videosuperposition of the detected pupil and the expected treatment geometry,for example, the lenticule diameter, flap diameter or the centers.

The invention can also be used in excimer laser systems in which thechange in shape of the cornea is carried out by ablation of the cornea.In this case, the object is not to position the patient in relation tothe therapy optics with high precision, since the therapeutic deviceusually compensates for slight inaccuracies in positioning by adjustingthe beam position by an amount of deviation measured by movementtracking; however, the comparison in terms of shape and position betweenthe shape and/or size of the detected pupil and the surgical structureto be implemented—an ablation pattern in the case of excimer lasers—canalso be used in treatment methods of this kind to improve thereliability and efficiency of the treatment. In this case again, it isuseful to omit illumination in the visible spectral region and to useinfrared illumination in order to correctly detect the optical zoneapplicable to the night vision of the patient.

In another embodiment, other features of the eye are also detected, forexample, iris structures. They are used to compare the relativerotational position of the eye with similar information from diagnosticmeasurements in order to determine relative rotation and relativedisplacement in relation to a diagnostic image (register image) in thisway.

In another embodiment, this information is used to carry out a rotationand/or displacement of the treatment geometry so as to compensate forthe relative rotation and/or displacement found in relation todiagnostic measurements.

In another embodiment, the detected features of the eye are compared toknown features of the eye of the scheduled patient to check the identityof the eye to be treated (eye recognition). In this case, theprobability of a mistake or the degree of identity found is displayed tothe user.

FIG. 3 shows two variants for centering a lenticule as structure S to begenerated: near the center of the photopic pupil P in FIG. 3A and nearthe center of the scotopic pupil P′ in FIG. 3B. It will be seen that incase A the lenticule and scotopic pupil P′ just barely overlap. Whenavailed of the inventive solution, the operator will be able to make anexact evaluation of these and similar situations in the available time.

For a description of the generation of the laser beam, reference is hadto WO 2008/055604 A1, particularly FIGS. 6 and 7 and the accompanyingdescription.

While this invention has been described in conjunction with the specificembodiments outlined above, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart. Accordingly, the preferred embodiments of the invention as setforth above are intended to be illustrative, not limiting. Variouschanges may be made without departing from the spirit and scope of theinventions as defined in the following claims.

LIST OF REFERENCE NUMERALS

-   1 laser treatment device-   2 support device-   3 treatment laser-   4 positioning device-   5 treatment head-   6 observation eyepiece-   7 control unit-   8 keypad-   9 monitor-   10 contact element-   11 detection device-   12 light source-   13 beamsplitter-   14 beamsplitter-   15 observation beam path-   19 beamsplitter-   20 evaluating unit-   A eye-   B video image-   P pupil-   S surgical structure

1. An ophthalmological laser treatment device comprising: a femtosecondlaser configured to introduce energy into a portion of an eye of apatient according to a predetermined surgical structure; a light sourceconfigured to illuminate at least the portion of the eye; a detectiondevice configured to record an image of at least the portion of the eye;an evaluating unit which is configured to determine a degree of aninstantaneous overlap between an optical zone of the eye and thepredetermined surgical structure or at least a part of the predeterminedsurgical structure effecting refractive correction based on a recordedimage; and a contact element for mechanically fixating the eye.
 2. Theophthalmological treatment device according to claim 1; wherein theevaluating unit is configured to determine an area of a pupil based onthe recorded image and an area of the predetermined surgical structure,or at least of the part of the predetermined surgical structureeffecting refractive correction, and an intersection between the twoareas.
 3. The ophthalmological treatment device according to claim 1;wherein the evaluating unit is configured to identify and locate acharacteristic of the eye in the recorded image and to determine arelative offset between a point of the characteristic and a point of thepredetermined surgical structure.
 4. The ophthalmological treatmentdevice according to claim 3; wherein the evaluating unit displays therecorded image visually in superposition with a graphic representationof the predetermined surgical structure according to the determinedoffset.
 5. The ophthalmological treatment device according to claim 2,further comprising: a support device for the patient and a positioningdevice configured to displace the support device and/or the laser;wherein the evaluating unit controls the positioning device depending onthe determined degree of overlap between the pupil and the predeterminedsurgical structure.
 6. The ophthalmological treatment device accordingto claim 1; wherein the evaluating unit compares a value of thedetermined degree of overlap to a predetermined threshold and outputs ahaptic and/or visual and/or acoustic signal depending on a result of thecomparison; and/or wherein the evaluating unit compares a value of thedetermined degree of overlap to a predetermined threshold value and,depending on a result of the comparison, carries out an irradiation ofthe eye corresponding to the predetermined surgical structure
 7. Amethod for introducing energy into an eye according to a predeterminedsurgical structure by means of a femtosecond laser, the methodcomprising the following steps: mechanically fixating the eye;determining, based on a recorded image, a degree of instantaneousoverlap between an optical zone of the eye and the predeterminedsurgical structure, or at least a part of the predetermined surgicalstructure effecting refractive correction; and taking the determineddegree of instantaneous overlap into account in at least one of: a stepof determining irradiation control data; and a step of deciding on acommencement of irradiation of the eye; wherein the degree ofinstantaneous overlap is determined before and/or after the mechanicalfixating is carried out.
 8. The method according to claim 7; wherein atleast one of the following steps is carried out for determining thedegree of instantaneous overlap: recording an image of the eye by meansof a detection device; identifying the pupil in the recorded image; anddetermining an area of the pupil based on the recorded image anddetermining an area of the predetermined surgical structure, or at leastof the part of the predetermined surgical structure effecting refractivecorrection, and then determining an intersection of the two areas. 9.The method according to claim 8; wherein the eye is illuminated withinfrared light, or wherein the eye is illuminated with visible light forrecording the; and wherein an intensity of the light is determined and,based on an instantaneous area of the recorded image and on theintensity, a maximum pupil area is predicted and is used for determiningthe overlap.
 10. The method according to claim 7; wherein thepredetermined surgical structure is displaced and/or enlarged until acomplete overlapping with the pupil is predicted.
 11. A control unitconfigured to implement the method according to claim
 7. 12. Theophthalmological treatment device according to claim 1; wherein thepredetermined surgical structure has a center of symmetry in which thereare no locations to be irradiated.
 13. The ophthalmological treatmentdevice according to claim 3, further comprising: a support device forthe patient and a positioning device configured to displace the supportdevice and/or the laser; wherein the evaluating unit controls thepositioning device depending on the offset between the characteristicand the predetermined surgical structure.
 14. The method according toclaim 7; wherein the predetermined surgical structure has a center ofsymmetry in which there are no locations to be irradiated.
 15. Anophthalmological laser treatment device comprising: a treatment laserconfigured to introduce energy into a portion of an eye of a patientaccording to a predetermined surgical structure; a light sourceconfigured to illuminate at least the portion of the eye; a control unitconfigured to record an image of at least the portion of the eye, and todeduce an actual relative offset of the eye with respect to thepredetermined surgical structure; and an evaluating unit which isconfigured to determine a degree of an instantaneous overlap between anoptical zone of the eye and the predetermined surgical structure or atleast a part of the predetermined surgical structure effectingrefractive correction based on a recorded image.
 16. Theophthalmological treatment device according to claim 15; wherein theevaluating unit is configured to determine an area of a pupil based onthe recorded image and an area of the predetermined surgical structure,or at least of the part of the predetermined surgical structureeffecting refractive correction, and an intersection between the twoareas.
 17. The ophthalmological treatment device according to claim 15;wherein the evaluating unit is configured to identify and locate acharacteristic of the eye in the recorded image and to determine arelative offset between a point of the characteristic and a point of thepredetermined surgical structure.
 18. The ophthalmological treatmentdevice according to claim 17; wherein the evaluating unit displays therecorded image visually in superposition with a graphic representationof the predetermined surgical structure according to the determinedoffset.
 19. The ophthalmological treatment device according to claim 16,further comprising: a support device for the patient and a positioningdevice configured to displace the support device and/or the laser;wherein the evaluating unit controls the positioning device depending onthe determined degree of overlap between the pupil and the predeterminedsurgical structure.
 20. The ophthalmological treatment device accordingto claim 15; wherein the evaluating unit compares a value of thedetermined degree of overlap to a predetermined threshold and outputs ahaptic and/or visual and/or acoustic signal depending on a result of thecomparison; and/or wherein the evaluating unit compares a value of thedetermined degree of overlap to a predetermined threshold value and,depending on a result of the comparison, carries out an irradiation ofthe eye corresponding to the predetermined surgical structure
 21. Theophthalmological treatment device according to claim 15, furthercomprising: a contact element for mechanically fixating the eye.
 22. Amethod for introducing energy into an eye according to a predeterminedsurgical structure by means of an excimer laser or a femtosecond laser,the method comprising the following steps: deducing, based on a recordedimage, an actual relative offset of the eye with respect to thepredetermined surgical structure; determining, based on the recordedimage, a degree of instantaneous overlap between an optical zone of theeye and the predetermined surgical structure, or at least a part of thepredetermined surgical structure effecting refractive correction; andtaking the determined degree of instantaneous overlap into account in atleast one of: a step of determining irradiation control data; and a stepof deciding on a commencement of irradiation of the eye.
 23. The methodaccording to claim 22; wherein at least one of the following steps iscarried out for determining the degree of instantaneous overlap:recording an image of the eye by means of a control unit; identifyingthe pupil in the recorded image; and determining an area of the pupilbased on the recorded image and determining an area of the predeterminedsurgical structure, or at least of the part of the predeterminedsurgical structure effecting refractive correction, and then determiningan intersection of the two areas.
 24. The method according to claim 23;wherein the eye is illuminated with infrared light, or wherein the eyeis illuminated with visible light for recording the; and wherein anintensity of the light is determined and, based on an instantaneous areaof the recorded image and on the intensity, a maximum pupil area ispredicted and is used for determining the overlap.
 25. The methodaccording to claim 22; wherein the predetermined surgical structure isdisplaced and/or enlarged until a complete overlapping with the pupil ispredicted.
 26. The method according to claim 22; wherein the eye ismechanically fixated; and wherein the degree of instantaneous overlap isdetermined before and/or after the mechanical fixating is carried out.27. A control unit configured to implement the method according to claim22.
 28. The ophthalmological treatment device according to claim 15;wherein the predetermined surgical structure has a center of symmetry inwhich there are no locations to be irradiated.
 29. The ophthalmologicaltreatment device according to claim 17, further comprising: a supportdevice for the patient and a positioning device configured to displacethe support device and/or the laser; wherein the evaluating unitcontrols the positioning device depending on the offset between thecharacteristic and the predetermined surgical structure.
 30. The methodaccording to claim 22; wherein the predetermined surgical structure hasa center of symmetry in which there are no locations to be irradiated.